Polyurethane foams are typically prepared in large buns which are cured and sliced into sections for uses such as cushions, etc. A problem particularly in summer months is that heat of reaction in the center of the bun is not adequately dissipated and may result in scorching or loss of desirable physical characteristics. Moreover, scorching problems are frequently aggravated by the presence of halogenated phosphate ester type flame retardants.
U.S. Pat. No. 4,143,219 discloses the use of phenothiazine to reduce scorch discoloration in polyurethane foams containing halogenated phosphate ester flame retardants.
U.S. Pat. No. 4,324,865 discloses the use of phenothiazine in combination with 4,4'-thio-bis-(6-tertiary butyl meta cresol) to reduce scorch discoloration in polyurethane foams containing halogenated phosphate ester flame retardants.
The foams, foam making methods and flame retarding compositions disclosed in U.S. Pat. Nos. 4,143,219 and 4,324,865 were improvements over prior art practice. Nevertheless, it is desirable to develop even more effective scorch and discoloration resistant agents.